A place like the Right Livers' Rest was bound to draw freaks, same as molasses draws flies. 1935, George Goodchild, chapter 5, in Death on the Centre Court: By one o'clock the place was choc-a-bloc.
Swallowing certain types of poisons may cause excessive salivation. According to the National Library of Medicine, pesticides can cause excessive saliva when they are swallowed. Venom from snake bites or insect stings is another type of poisoning that can cause the malady.
Any disorder affecting nerves associated with the mouth or throat can result in excessive saliva, either because more is being produced, or because of difficulties in swallowing, more is being stored in the mouth.